as in treacherous
formal
causing harm in a way that is gradual or not easily noticed
Most people with this insidious disease have no idea that they are infected. an insidious enemy
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Example Sentences
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Recent Examples of insidious
An insidious fear is reaching through our schools, our businesses, our homes and into our private thoughts.
—
Ted Johnson, Deadline, 7 June 2025
Pervasively unsettling, both too alien and too familiar, Hunting in America coolly illustrates the complicity that both Israeli and Americans have in a gun-touting culture, and the insidious ways that violence can seep into our consciousness.
—Emily Temple
may 27, Literary Hub, 27 May 2025
The Effort-Reward Disconnect Perhaps the most insidious barrier to preparation is the invisibility of its benefits.
—Roy Ward, Forbes.com, 16 May 2025
What’s insidious in her philosophy is the notion that good choices and a positive attitude can obviate the need for modern pharmaceuticals.
—Michelle Goldberg, Mercury News, 15 May 2025
See All Example Sentences for insidious
Ted Johnson, Deadline, 7 June 2025
Pervasively unsettling, both too alien and too familiar, Hunting in America coolly illustrates the complicity that both Israeli and Americans have in a gun-touting culture, and the insidious ways that violence can seep into our consciousness.
—Emily Temple
may 27, Literary Hub, 27 May 2025
The Effort-Reward Disconnect Perhaps the most insidious barrier to preparation is the invisibility of its benefits.
—Roy Ward, Forbes.com, 16 May 2025
What’s insidious in her philosophy is the notion that good choices and a positive attitude can obviate the need for modern pharmaceuticals.
—Michelle Goldberg, Mercury News, 15 May 2025
See All Example Sentences for insidious
Recent Examples of Synonyms for insidious
Adjective
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The storm could bring hazardous travel, power outages, and treacherous trail conditions during a time of year typically dominated by warmer weather and early summer tourism.—
Martha McHardy,
MSNBC Newsweek,
19 June 2025
-
Having heard rumors of a mythical doctor (played with a chilling calm by Ralph Fiennes) who could possibly help, Spike sneaks off with her for a treacherous expedition to the mainland.—
Mark Olsen,
Los Angeles Times,
18 June 2025
Adjective
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In this edition, the grey tone reflects the muted, misty landscape of the British coast, with subtle variations achieved through multiple layers of transparent lacquer.—
Matthew Catellier,
Forbes.com,
30 June 2025
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The result was a robust workforce forecasting model, one that’s sophisticated enough to consider the subtle complexities of human behavior and help identify potential attrition risks.—
Nia Bowers,
USA Today,
30 June 2025
Adjective
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Simultaneously, Dani Olmo could act as a false number 9 while a Robert Lewandowski believed to be on his way to Saudi Arabia in 2026 is gradually phased out.—
Tom Sanderson,
Forbes.com,
24 June 2025
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But an investigation resulted in an astonishing call from the other side of the world, which revealed that ‘The GPO Girl’ was, in fact, a 25-year-old Australian, who has created more than 100 false identities.—
Max Goldbart,
Deadline,
24 June 2025
Adjective
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In the suit, filed Friday, Newsom says that Fox News had used deceptive edits to claim that the governor had lied in saying that Trump had not called him about deploying National Guard troops during the L.A. protests.—
Caitlin Huston,
HollywoodReporter,
27 June 2025
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Florida is leading the way in what can become a national movement to crack down on hospitals’ deceptive and unfair billing practices.—
Cynthia A. Fisher,
Sun Sentinel,
26 June 2025
Adjective
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Those voting for it are Sean Elo-Rivera, Jennifer Campbell, Kent Lee, Stephen Whitburn, Vivian Moreno and La Jolla’s own Joe LaCava, who has been an active supporter of this perfidious plan.—
Inga,
San Diego Union-Tribune,
16 June 2025
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Jake Gyllenhaal is his foil as the perfidious Iago, who goads Othello into unreasoning jealousy with lies about his beloved Desdemona (Molly Osborne).—
New York Times,
New York Times,
17 Feb. 2025
Adjective
-
Consider a car engine: Removing deposits and sludge (inaccurate, outdated, irrelevant and incorrect information) reduces friction, while clean oil (large language models and AI) ensures smooth performance.—
Savinay Berry,
Forbes.com,
26 June 2025
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Belief in other scientifically incorrect claims can be extremely dangerous.—
Mark Boslough,
Scientific American,
25 June 2025
Adjective
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The end of season 2 turned the tables on the meek Ada and domineering Agnes when Agnes lost her fortune thanks to her son Oscar (Blake Ritson) trusting the wrong people.—
Maureen Lee Lenker,
EW.com,
23 June 2025
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The Verge reported a Tesla Model Y robotaxi briefly traveled the wrong way down a road in Austin.—
Samantha Subin,
CNBC,
23 June 2025
Cite this Entry
“Insidious.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/insidious. Accessed 4 Jul. 2025.
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